1. Field of the Invention
The invention is a perpendicular recording head for use with magnetic storage media. The perpendicular recording head has a tip with a concave surface for concentrating the magnetic flux over a smaller portion of the magnetic storage medium""s surface area than current perpendicular recording heads.
2. Description of the Related Art
Although other perpendicular recording heads have been developed, the present invention improves upon presently known perpendicular recording heads by utilizing a concave cavity to focus magnetic flux, or being dimensioned and configured to focus magnetic flux at a distance approximating the flying height of the recording head.
An example of a magnetic recording head is described in U.S. Pat. No. 4,078,300, issued to J. P. Lazzari on Mar. 14, 1978. This patent describes a method of making a magnetic recording head intended to work in conjunction with a track of a magnetic storage medium having a narrow width.
U.S. Pat. No. 4,138,702, issued to J. G. Magnenet on Feb. 6, 1979, describes a head arrangement for perpendicular recording on a magnetic record carrier. The head arrangement has an electromagnet with a core and a magnetic shunt on opposite sides of the magnetic recording medium.
U.S. Pat. No. 4,546,398, issued to J. Toda et al. on Oct. 8, 1985, describes a perpendicular recording head. The perpendicular recording head includes a main pole made from a thin magnetic film, and a spiral coil electromagnetically coupled to the main pole.
U.S. Pat. No. 4,652,956, issued to H. Schewe on Mar. 24, 1987, describes a recording head for perpendicular magnetization. The recording head has a pair of magnetic legs forming a ring-shaped member, and separate read and write wire coils. The read coil is located between the two magnetic legs, and the write coil is located outside one of the two magnetic legs.
U.S. Pat. No. 4,731,157, issued to J. P. Lazzari on Mar. 15, 1988, describes a process for making a perpendicular recording head. The process includes the steps of depositing magnetic film on an insulating substrate, etching a channel in the magnetic film for containing a coil within a dielectric material, etching another channel in the dielectric layer for containing a second magnetic film, removing dielectric material to expose the lateral edge of the second magnetic film, and depositing additional dielectric material on top of the second magnetic film.
U.S. Pat. No. 4,943,882, issued to T. Wada et al. on Jul. 24, 1990, describes a perpendicular recording head. The recording head includes a first main pole surrounded by a conductor coil, with an insulator covering the first main pole and coil. The first main pole is in contact with a magnetic substrate at its top end. A second main pole is in contact with the first main pole. This assembly is covered with a protective overcoat. A similar recording head is described in U.S. Pat. No. 5,225,953, also issued to T. Wada et al. on Jul. 6, 1993.
U.S. Pat. No. 4,974,110, issued to M. Kanamine et al. on Nov. 27, 1990, describes a perpendicular recording head having a main magnetic pole, a spiral coil surrounding the main pole, and a pair of auxiliary magnetic poles on either side of the main pole. The magnetic flux from the resulting two magnetic leakage paths and the coil cancel each other out, thereby reducing edge noise.
U.S. Pat. No. 4,985,792, issued to M. B. Boir on Jan. 15, 1991, and assigned to the assignee of the present inventors, describes an improved spindle motor for a fixed disk drive for a computer.
U.S. Pat. No. 5,035,396, issued to R. G. Krum et al. on Jul. 30, 1991, and assigned to the assignee of the present inventors, describes a disk drive having a sealed disk drive housing, a common chassis for the disk drive and printed circuit board, and a floating bushing connecting the circuit board to the disk drive housing.
U.S. Pat. No. 5,073,836, issued to H. S. Gill et al. on Dec. 17, 1991, describes a perpendicular recording head. The primary magnetic pole is separated from the auxiliary pole by a distance sufficient to increase the reluctance of the recording head, thereby minimizing erasure of data within the recording medium.
U.S. Pat. No. 5,241,430, issued to D. W. Janz on Aug. 31, 1993, and assigned to the assignee of the present inventors, describes a disk drive which accepts write operations during manufacture, but only accepts read operations in use. The drive""s controller responds to power supply voltage levels available to the user""s computer by performing only read operations, but will perform a write operation in response to a higher voltage.
U.S. Pat. No. 5,430,589, issued to M. B. Moir et al. on Jul. 4, 1995, and assigned to the assignee of the present inventors, describes a disk drive having a vibration-absorbing insulator between the housing and the shaft for the storage disks.
U.S. Pat. No. 5,486,967, issued to Y. Tanaka et al. on Jan. 23, 1996, describes a perpendicular recording head having a pair of main poles, and which is in contact with the magnetic disk during use.
U.S. Pat. No. 5,738,927, issued to A. Nakamura et al. on Apr. 14, 1998, describes a perpendicular magnetic recording medium having a substrate and a film having perpendicular magnetic anisotropy formed over the substrate. A protective film covers the magnetic film.
U.S. Pat. No. 5,796,557, issued to G. N. Bagnell et al. on Aug. 18, 1998, and assigned to the assignee of the present inventors, describes a disk drive including six storage disks and fitting within a 3.5 inch, half height port.
U.S. Pat. No. 5,996,045, issued to L. Lee et al. on Nov. 30, 1999, and assigned to the assignee of the present inventors, describes a disk drive arrangement combining a master drive and a slave drive. Both drives use the same IDE bus. The host computer is able to send commands over the IDS bus in the same manner as if only one disk drive was present, and the command is then carried out by the appropriate drive.
The article, Sakhrat K. Khizroev, James A. Bain, and Mark H. Kryder, xe2x80x9cConsiderations in the design of Probe Heads for 100 Gbit/in2 Recording Density,xe2x80x9d IEEE Transactions on Magnetics (September, 1997) pp. 2893-2895, describes work performed by two inventors of the present invention towards development of giant magnetoresistive read heads capable of reading magnetic storage media having high storage densities.
The article, Jon William Toigo, xe2x80x9cAvoiding a Data Crunch,xe2x80x9d Scientific American (May, 2000) pp. 58-74, describes several approaches to increasing the information storage density within fixed computer drives.
None of the above described patents and publications describes a perpendicular recording head for use with magnetic recording media having a concave cavity at its tip for concentrating the magnetic flux within the storage layer of the magnetic storage medium. Additionally, none of the above patents and publications describes a recording head permitting the recording densities possible with the present invention.
The present invention is a perpendicular recording head for use with magnetic recording media having a main pole with a tip having a concave surface. The concave surface concentrates magnetic flux from the main pole to a higher density than a conventional perpendicular recording head at a distance approximating the flying height of the head, thereby permitting a greater amount of information to be stored on the magnetic recording medium. Although not limited to such use, a perpendicular recording head of the present invention is particularly useful for fixed (also known as hard) computer disk drives.
A typical perpendicular recording head includes a main pole, an opposing pole magnetically coupled to the main pole, and an electrically conductive wire coil surrounding the main pole. The bottom of the opposing pole will typically have a surface area greatly exceeding the surface area of the main pole""s tip. Electrical current flowing through the coil creates a flux through the main pole. The direction of the flux may be reversed by reversing the direction of current flow through the coil.
A typical magnetic recording medium for use in conjunction with a perpendicular recording head includes an upper layer having a plurality of magnetically permeable tracks separated by nonmagnetic transitions, and a magnetically permeable lower level. The lower level is magnetically soft relative to the tracks.
To write to the magnetic recording medium, the recording head is separated from the magnetic recording medium by a distance known as the flying height. The magnetic recording medium is moved past the recording head so that the recording head follows the tracks of the magnetic recording medium, with the magnetic recording medium first passing under the opposing pole and then passing under the main pole. Electricity is passed through the coil to create magnetic flux within the main pole. The magnetic flux will pass from the main pole through the track, into the lower layer, and across to the opposing pole. The flux will thereby cause the magnetic fields in the tracks to align with the magnetic flux of the recording head. Changing the direction of electric current changes the direction of the flux created by the recording head and therefore the magnetic fields within the magnetic recording medium. Because the surface area of the opposing pole is significantly greater than the surface area of the main pole, only the main pole will have a sufficient concentration of magnetic flux to influence the magnetic fields in the magnetic recording medium.
Reading from the magnetic recording medium follows the opposite procedure. The magnetic flux of the magnetic recording medium will pass through the main pole as the main pole is passed over the recording medium. Whenever there is a change in the magnetic fields of the recording medium, the flux within the main pole will change accordingly. Such changes in flux will induce a current within the coil. Alternatively, a magnetoresistive or giant magnetoresistive read head may be used with the present invention.
The density with which information may be recorded on the magnetic recording medium is limited by the effect of the recording head""s magnetic flux on neighboring regions of the magnetic recording medium during read and write operations. Each discrete sector of the magnetic recording medium must be sufficiently distant from neighboring sectors so that magnetic flux from the recording head will only affect that sector which the recording head is directly over. A typical perpendicular recording head, having a flat tip, will create a significant amount of flux spreading out towards the surrounding sectors. The present invention minimizes this problem by using a head with a concave tip.
It is well known in physics that magnetic flux passing through the surface of magnetically permeable material will always be perpendicular to that surface. Therefore, magnetic flux passing through a flat main pole tip will exit the pole tip with all flux lines being parallel. After exiting the pole tip, the flux lines will then tend to diverge from each other. By using a concave main pole tip, the flux lines are first focused a short distance from the main pole tip, thereby preventing them from diverging from each other within the short distance from the pole tip through the magnetic storage medium""s upper layer. By concentrating the magnetic flux on a smaller area of the magnetic recording medium, the recording medium may use smaller sectors without the recording head influencing the magnetic field of more than one sector at a time, thereby permitting more sectors to be contained on a disk.
In a most preferred embodiment, the main pole tip""s concave cavity in the main pole tip will have a curved cross section when viewed from any side, for example, ellipsoidal or hemispherical. Such a cross section may be dimensioned and configured to concentrate magnetic flux within the center of the magnetic recording medium""s upper level when the recording head and recording medium are separated by the flying height of the recording head.
It is therefore an aspect of the present invention to provide a perpendicular recording head defining a cavity at the tip of the main pole.
It is another aspect of the present invention to provide a perpendicular recording head being dimensioned and configured to concentrate magnetic flux within the magnetic recording medium.
It is a further aspect of the present invention to provide a perpendicular recording head defining a concave, ellipsoidal or hemispherical cavity.
It is another aspect of the present invention to provide a magnetic recording apparatus wherein information can be stored at greater densities.
It is a further aspect of the present invention to provide a magnetic recording apparatus wherein a magnetic recording medium having a higher level of coercivity may be utilized.
It is another aspect of the present invention to provide a perpendicular recording head having a higher sensitivity during read operations.
It is a further aspect of the present invention to provide a method of storing data on a magnetic storage medium utilizing a perpendicular recording head of the present invention, thereby providing for higher information storage densities than were possible with other recording heads.
It is another aspect of the present invention to provide a method of manufacturing a perpendicular recording head adapted to permit recording on magnetic storage media at higher information densities than were available in the past.
These and other aspects of the invention will become more apparent through the following description and claims.